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coondoggie writes "On its current space scouting mission, NASA's Lunar Reconnaissance Orbiter (LRO) is using a pumped up communications device to deliver 461 gigabytes of data and images per day, at a rate of up to 100 Mbps.
As the first high data rate K-band transmitter to fly on a NASA spacecraft, the 13-inch-long tube, called a Traveling Wave Tube Amplifier, is making it possible for NASA scientists to receive massive amounts of images and data about the moon's surface and environment.
The amplifier was built by L-3 Communications Electron Technologies in conjunction with NASA's Glenn Research Center. The device uses electrodes in a vacuum tube to amplify microwave signals to high power. It's ideal for sending large amounts of data over a long distance because it provides more power and more efficiency than its alternative, the transistor amplifier, NASA stated." It kills me that the moon has better bandwidth than my house.

My question is why you need a vacuum tube in a vacuum? Just put the parts out in open space, save a bit of weight, no problem with the tube getting deposits on it over time, or thermal expansion and contraction stressing the tube, etc.

You're laboring under the idea that space is empty. But it's not, and throwing highly charged particles around (required for RF transmission) is going to attract the wrong kind of folk to the party. -_-

--In reality with 10Mbit link, you'd be lucky to get ~850-900KB/sec for an FTP transfer over a small LAN, in real-world speeds. ( From what I recall ) Feel free to correct if you have a real-world story...

"In space, no one can eat ice cream"? (One of the not best b grade movies)

And what the hell? Vacuum tubes over transistors? Seriously? Are they super vacuum-ized because they are used in the vacuum of space? Makes me think of one of those medical shows where a surgeon is like "we need more suction". Vacuums FTW!

Vacuum tubes have always had higher frequency limits than transistors, since WWII in fact. Take a look at THz radiation sources, all tubes. No tranny is going to touch that for a while. And then tubes will have gotten better too.http://en.wikipedia.org/wiki/Backward_wave_oscillatorTubes just have more geometric freedoms to create bizarre fields and strange structures to do whatever you need.

Traveling Wave Tubes have been a mainstay of microwave communications and radar systems for the better part of a century. They're a very efficient way of amplifying microwave signals to the very high power levels needed to cross long distances.

The article admits that the Traveling Wave Tubes are not new, but it also lists several points that make this implementation better and very much noteworthy compared to its predecessors. You seem to have an interest in/knowledge of these communication devices, so I would say that the article is actually a worthwhile read for you.

Yes. But it's not easy. A TWT is, in many ways, very similar to a linear acclerator, except that instead of using RF to put energy into an electron beam to make it faster, it takes energy out of a fast electron beam to amplify an RF signal. So whip out those books on linear accelerator design and construction, and have at it. You need an electron gun and some electron optics to make the beam, and then the section where the RF interacts with the beam, either a helix or a series of coupled resonant cavitie

Actually, try getting a ham license and you will find plenty of equipment and help experimenting with microwaves. I regularly see TWTs, brick oscillators [nr6ca.org], http://home.swbell.net/k5oe/K-Band/K-Band.htm [slashdot.org]">K-band (24 GHz) and X-band (10 GHz) equipment in the under $100 price range. Even the old Gunn Diode Oscillators can provide some fun [youtube.com]. Hams even launch their own satellites [amsat.org] and send their own microwave [home.wxs.nl] and VHF/UHF signals [youtube.com] to the moon and back.

Yes it is old tech but frankly that makes it all the more interesting in a way.It is a tube and not solid state.And now here is the joke that I know must come.If we used these for wireless internet then it really would be a bunch of tubes.Sorry but it had to be done..

And these have been used in space applications since the early 60's. In fact every satellite program that I have worked on used TWTA amplifiers. People are always looking for alternatives because they are very squirrely devices, but it's pretty difficult to generate much power at microwave frequencies with solid-state alternatives.

Exactly. Why the hell does the summary go into depth on TWT's? They've been around since WWII, and have been extensively forever.

Cause Joe Sixpack never heard of them? And with the possibility of NASA losing some more budget [newscientist.com], it's best to keep talking up all that cool tech that's been around since the Stone Age, makes people think you just found something cool.

When you need to make serious power, tubes are still the way to go. Transistors have a significant reliability benefit.

Also, for 99% of applications, transistors are better. For the other 1%, you have very application-specific tube designs such as TWTs and magnetrons, which rearrange the tubes in such a manner as to negate its usual disadvantage (large size USUALLY translates to nasty frequency limits - TWTs and magnetrons are exceptions that use various Neat Tricks to allow microwave operation from a large device.)

BTW, one of the other common microwave tubes (magnetrons), while it is a "niche" device, it is a VERY widely deployed niche - basically all microwave ovens use magnetron tubes.

I think he was referring to the "vacuum" of space. Why not just take the glass off the outside and save some weight?

Because the tube would get contaminated by the pollutants & particles in the atmosphere, and some of that won't outgas as the probe gets into a decent vacuum. Also, the solar wind [wikipedia.org] kicks particles out as well, and some of those could also contaminate the tube, threatening its lifespan and/or performance.

curious thing about tubes, they don't become useful until they're sealed in vacuum, and boiled out in a high RF magnetic field to take impurities off the elements. and then you have to flash the last of the gases off by igniting a getter inside the envelope.

that provides a higher vacuum on earth, inside the tube, than you can ever develop in space. and the electrons can do their work, instead of hitting stuff and just making a useless glow.

At an old company, our lead tech kept talking about how to configure one of our digital scanners, using the acronym for "Scanner Look-Up Table"... even writing it in big, bold letters on the board. Being a 50+year-old Vietnamese guy, it didn't mean anything to him, and he just kept on going.

We peed ourselves laughing... our boss didn't when he walked into the room to see a huge "SLUT" written on the board.:)

That much data and Comcast would throttle it no matter what the scientists said. If AT&T had it going through their "unlimited" 3G connection, NASA would be hosed and we would be increasing the national debt by trillions.

One last thing, I m wondering if the **AA doesn't want access to the data stream to make sure it isn't a bittorrent containing their precious copyrighted work. After all, we all know there is no legitimate use for that much bandwidth.

TWT amps have been used in microwave systems since the 2nd world war. The use of TWT in satellites are recent, as in 25-30 years ago. The NSA's LACROSSE and the new ONYX satellites use TWT amps in the finals on their radar systems. The Soviet ROARSAT's probably use them as well, or something similar, they love to overbuild their stuff.

Hell, the YF-12a used 2 TWT's in tandem in its Hughes AN/ASG-18 radar, putting out over 10MW of raw power.

But they are power gobblers, The YF-12A's ate over 40KVA of juice to operate.

On July 10, 1962, the first communications satellite, Telstar 1, was launched with a 2 W, 4 GHz RCA-designed TWT transponder used for transmitting RF signals back to the earth. Syncom 2, the first synchronous satellite (Syncom 1 did not reach its final orbit), launched on July 26, 1963 with two 2 W, 1850 MHz Hughes-designed TWT transponders (one active and one spare).

I know that Taco's trying to be funny here, but, seriously, the moon should most certainly have better bandwidth. That is to say, a research project that is able to afford a custom solution to a highly specialized problem with plenty of money to throw at had damned well better have better performance than what is available to commodity markets. I expect this to be true just as nearly every other bit of the hardware they send up will be better, faster, stronger, lighter, and more able to withstand ionizing radiation than the equivalent, when available, from K-Mart. There's a good reason these projects cost hundreds of millions of dollars for a probe to be sent somewhere. The Mars rovers, as another example, are using a 256 kbps channel -- deployed five years ago when DSL was still considered fast -- over a distance that ranges 55 to 400 million miles. Now *that's* performance.

It actually rather amazes me that Taco's or anyone else's house has close to the bandwidth available from the moon.

In fact the limited factor is recording speed and capacity. The large atom-smashers run the receptor data through a preliminary A.I. discrmination programs which save the small fraction deemed interesting. Then slaving grad students will spend years on tiny pieces extacting the significant discoveries.

Some of the large ground telescopes are partnering with Google and MicroSoft to put large portions of their data online. The computer programs and main scientists only have enough time to give a cursory glance at it. Maybe it will be a kid in a junior high school science lab that looks at something more closely and makes a discovery. Some of this is occuring with google earth imagery now.

but for high power, squirrelly conditions, and reliability under real world conditions, tubes are still the go-to player in a lot of situations. a solar storm will roach semiconductor outputs, but it takes a monster pulse straight down the gullet to take a tube out.

You know what's ironic?I HAVE played WoW with over a second of lag.Fuck, sometimes WoW servers were having up to fucking three seconds lag. It's rare, but it always happens at the worst possible moment, often during a boss fight.

If I was stuck on the moon with absolutely nothing to do, I wouldn't complain about 1 second of lag if WoW was my only source of daily fun.

Um....Not sure if you're trolling or serious.Video (especially progressive scan stuff) is nothing but a sequence of pictures.

Color photos are wasteful of imaging sensor resolution.To make a color photo you have to filter the light that hits the image sensor, either the way home digicams do it (RGBG filtering over individual pixels, thus 1/4 of your raw sensor resolution is available for final image resolution), or the way instrumentation cameras do it: Spin a color wheel (RGB) in front of your sensor eleme

that level of bandwidth availability may not equal its use. And as someone who has a 100Mbps connection i realistically only see about 50-70Mbps. I dont have any sort of service level agreement with my ISP, and i can pretty much guarantee neither does NASA, afterall its space. so if they're net result is a daily avearge of 46Mbps of data thats pretty awesome considering all the variables that would determine the total bandwidth.

Since it's orbiting I expect that it has a blackout period similar to that encountered by the Apollo spacecraft. Makes sense that it would have as fast a link as possible to offload data before the next blackout period.

All this talk about bandwidth, I'm more interested in the amount of storage space needed back here on earth to store all that data being transferred. 461GB of data per day is around 3.2TB of data per week or a little less than 1.7 Petabytes of data per year (I think.. if my math is correct). Once you add in all of their other storage needs that's one hell of a SAN.

Probably not. Distorted electric guitar is an instrument, sure, but one that's only been around a few decades with few examples of musical genius. The vast majority of truely great guitar music ever written by mankind would sound like crap on an overcranked tube amp.